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Allow for IFDRational with negative numerator and zero denominator

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This commit is contained in:
Andrew Murray 2025-05-25 15:20:21 +10:00
parent 7e4d8e2f55
commit c8c6ff96e0
2 changed files with 19 additions and 36 deletions
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52
Tests/test_file_tiff_metadata.py
View File

@ -385,14 +385,21 @@ def test_ifd_unsigned_rational(tmp_path: Path) -> None:
assert 1 == reloaded.tag_v2[41493].denominator
def test_ifd_signed_rational(tmp_path: Path) -> None:
@pytest.mark.parametrize(
"numerator, denominator, expected",
(
(2**31 - 1, -(2**31), None), # pair of 4 byte signed longs
(-(2**31), 2**31 - 1, None),
(-(2**31) - 1, 1, (2**31 - 1, -1)), # out of bounds of 4 byte signed long
(-1, 0, None), # IFDRational nan
),
)
def test_ifd_signed_rational(
numerator: int, denominator: int, expected: tuple[int, int] | None, tmp_path: Path
) -> None:
im = hopper()
info = TiffImagePlugin.ImageFileDirectory_v2()
# pair of 4 byte signed longs
numerator = 2**31 - 1
denominator = -(2**31)
info[37380] = TiffImagePlugin.IFDRational(numerator, denominator)
out = tmp_path / "temp.tiff"
@ -400,35 +407,12 @@ def test_ifd_signed_rational(tmp_path: Path) -> None:
with Image.open(out) as reloaded:
assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
assert numerator == reloaded.tag_v2[37380].numerator
assert denominator == reloaded.tag_v2[37380].denominator
numerator = -(2**31)
denominator = 2**31 - 1
info[37380] = TiffImagePlugin.IFDRational(numerator, denominator)
out = tmp_path / "temp.tiff"
im.save(out, tiffinfo=info, compression="raw")
with Image.open(out) as reloaded:
assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
assert numerator == reloaded.tag_v2[37380].numerator
assert denominator == reloaded.tag_v2[37380].denominator
# out of bounds of 4 byte signed long
numerator = -(2**31) - 1
denominator = 1
info[37380] = TiffImagePlugin.IFDRational(numerator, denominator)
out = tmp_path / "temp.tiff"
im.save(out, tiffinfo=info, compression="raw")
with Image.open(out) as reloaded:
assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
assert 2**31 - 1 == reloaded.tag_v2[37380].numerator
assert -1 == reloaded.tag_v2[37380].denominator
if expected is None:
expected = (numerator, denominator)
assert (
reloaded.tag_v2[37380].numerator,
reloaded.tag_v2[37380].denominator,
) == expected
def test_ifd_signed_long(tmp_path: Path) -> None:

3
src/PIL/TiffImagePlugin.py
View File

@ -687,8 +687,7 @@ class ImageFileDirectory_v2(_IFDv2Base):
self.tagtype[tag] = TiffTags.UNDEFINED
if all(isinstance(v, IFDRational) for v in values):
for v in values:
assert isinstance(v, IFDRational)
if v < 0:
if v < IFDRational(0):
self.tagtype[tag] = TiffTags.SIGNED_RATIONAL
break
else: